It is well recognized that the cerebrovascular system plays a critical role in maintaining normal brain function. It is apparent that malfunctions in this system (e.g. due to aging, genetic factors, drugs and viral or autoimmune insults) would directly affect neural metabolism and function and could result in various brain pathologies. However, as yet, the mechanisms underlying the basic functioning and regulation of the cerebral microcirculation are not well understood. The proposed research is intended to further our understanding of the regulation of the cerebrovasculature by neurotransmitter systems through the use of in vitro biochemical and tissue culture techniques. In particular the questions of how neurotransmitter-vascular relationships vary in aging and in different brain regions will be addressed. Receptor binding sites, synthetic and degradative enzymes, and specific uptake an release processes for the transmitters acetylcholine, Gamma-aminobutyric acid, and norepinephrine will be measured in isolated brain microvessel preparations. Lesion experiments will be used to test the possibility that cerebral cortical vessels are innervated by cholinergic projections from basal forebrain, a pathway drastically reduced in Alzheimer's patients. Tissue culture techniques also will be used to obtain pure brain capillary endothelial cells in quantities sufficient for biochemical assay. Various properties of the cultured cells will be characterized and possible inductive effects of glia and other perivascular elements will be studied in culture. Enzymes and transport processes specifically associated with the blood-brain barrier (BBB) and thought to be located in the cerebrovascular endothelial cells will be assayed on culture. It is hoped that with the cultures a functioning in vitro model of the BBB will be established in order to directly study the effects of various substances on the permeability of this barrier. Hopefully, a better understanding of cerebrovascular transmitter systems and BBB properties, normally and as a function of aging, will provide a foundation for pharmacological approaches towards ameliorating symptions associated with aging of the brain.